This invention relates to an electronic fuel injection control system for multi-cylinder internal combustion engines, and more particularly to a fuel injection control system of this kind which is capable of obtaining smooth and positive starting of the engine.
An electronic fuel injection control system adapted for use with an internal combustion engine, particularly a gasoline engine has been proposed e.g. by U.S. Ser. No. 348,648 filed Feb. 12, 1982 by the assignee of the present application, which is adapted to determine the valve opening period of a fuel injection means for control of the fuel injection quantity, i.e. the air/fuel ratio of an air/fuel mixture being supplied to the engine, by first determining a basic value of the above valve opening period as a function of engine rpm and intake pipe absolute pressure and then adding to and/or multiplying same by constants and/or coefficients being functions of engine rpm, intake pipe absolute pressure, engine temperature, throttle valve opening, exhaust gas ingredient concentration (oxygen concentration), etc., by electronic computing means.
The above-proposed electronic fuel injection control system, when applied to a multi-cylinder internal combustion engine, is arranged such that injectors, which are each provided for each cylinder of the engine, are actuated in predetermined sequence in synchronism with pulses of a TDC signal indicative of the pistons passing predetermined positions relative to the top-dead-center (TDC) positions within the cylinders. Determination as to which cylinders the individual pulses of the TDC signal correspond to is made on the basis of the timing of generation of a cylinder-discriminating signal which is generated each time the crankshaft rotates through a predetermined angle, to thereby carry out fuel injection into the cylinders in predetermined sequence.
However, at the start of the engine, in most cases the above cylinder-discriminating signal is not generated immediately upon starting of the engine, depending upon the angular position of the crankshaft assumed immediately before the start of the engine. In such cases, there can occur a noncoincidence in timing between the suction stroke of a certain cylinder and the valve opening action of the corresponding injector, so that the supply of fuel into the cylinders is not effected smoothly, preventing smooth and positive starting of the engine.